Previous studies evaluated various risk factors for knee OA; however, no study has examined the association between spinal factors, such as total spinal alignment and spinal range of motion (ROM), with knee OA. The purpose of this study was to examine the influence of spinal factors including total spinal alignment and spinal ROM on knee OA in community-living elderly subjects. A total of 170 subjects ≥60 years old (mean age 69.4 years, 70 males and 100 females) enrolled in the study (Yakumo study) and underwent a basic health checkup. We evaluated A-P knee radiographs, sagittal parameters (thoracic kyphosis angle, lumbar lordosis angle, and spinal inclination angle) and spinal mobility (thoracic spinal ROM, lumbar spinal ROM and total spinal ROM) as determined with SpinalMouse(®). The radiological assessment of knee OA was based on the Kellgren and Lawrence classification, and the knee flexion angle was measured while the subject was standing. Spinal inclination angle and thoracic spinal ROM correlated significantly with knee OA on univariate analyses. Multivariate logistic regression analysis indicated that an increase in spinal inclination angle (OR 1.073, p<0.05) was significantly associated with knee OA. Spinal inclination angle had significant positive correlation with knee flexion angle (r=0.286, p<0.001). The spinal inclination angle is the most important factor associated with knee OA.

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